Place · Level 3 · Macros
Protein During a Deficit · the Muscle-Preservation Playbook
标准能量赤字下 25-30% 流失是瘦组织 · 1.6-2.4 g/kg 是金标准 · 高蛋白 + 抗阻 = Longland 2016 同时减脂增肌 · 每餐 25-40 g 分 3-4 餐
Story path
Chapter 1
Why weight loss ≠ fat loss
Why weight loss ≠ fat loss
When you lose weight, the body doesn't only burn fat. Under a standard energy deficit, roughly 25-30% of weight lost is lean tissue — including skeletal muscle, visceral protein, and water (Hall 2015). This isn't a malfunction; it's the body's default policy during energy shortage: tear down protein and fat together, because amino acids can feed gluconeogenesis for the brain, muscle contraction is metabolically expensive, and unused tissue is 'saved on'.
Why this is a problem:
RMR drops: muscle is the main consumer of resting metabolism. Losing 5 kg of muscle ≈ RMR ↓ 50-70 kcal/day. Combined with adaptive thermogenesis, the deeper the cut the lower the RMR, and the harder it gets.Strength and function decline: strength falls faster than muscle (neural drive + cross-section both lose).Rebound is harsher: body fat regenerates faster than muscle, so the regain is fat-first. Repeated cycles → progressively worse body composition (the precursor to 'sarcopenic obesity').
Longland 2016 landmark trial (McMaster, AJCN):
40 young men, 40% energy deficit (-40% TDEE) for 4 weeksAll performed high-intensity resistance + HIIT, 6 days/weekRandomised: high protein 2.4 g/kg vs control 1.2 g/kgResults:High-protein group: fat -4.8 kg, lean mass +1.2 kg (fat loss + muscle gain simultaneously)Control group: fat -3.5 kg, lean mass +0.1 kg (basically no change)Conclusion: under an extreme deficit, adequate protein + resistance training + sufficient training stimulus = lose fat and still build a little muscle
Key takeaway: muscle preservation isn't about 'how fast you lose'; it's about 'is protein enough + is there a signal the muscle can use (resistance training)'. Without those two, roughly 1/3 of the weight you drop is probably tissue you didn't want to lose.
Why this is a problem:
RMR drops: muscle is the main consumer of resting metabolism. Losing 5 kg of muscle ≈ RMR ↓ 50-70 kcal/day. Combined with adaptive thermogenesis, the deeper the cut the lower the RMR, and the harder it gets.Strength and function decline: strength falls faster than muscle (neural drive + cross-section both lose).Rebound is harsher: body fat regenerates faster than muscle, so the regain is fat-first. Repeated cycles → progressively worse body composition (the precursor to 'sarcopenic obesity').
Longland 2016 landmark trial (McMaster, AJCN):
40 young men, 40% energy deficit (-40% TDEE) for 4 weeksAll performed high-intensity resistance + HIIT, 6 days/weekRandomised: high protein 2.4 g/kg vs control 1.2 g/kgResults:High-protein group: fat -4.8 kg, lean mass +1.2 kg (fat loss + muscle gain simultaneously)Control group: fat -3.5 kg, lean mass +0.1 kg (basically no change)Conclusion: under an extreme deficit, adequate protein + resistance training + sufficient training stimulus = lose fat and still build a little muscle
Key takeaway: muscle preservation isn't about 'how fast you lose'; it's about 'is protein enough + is there a signal the muscle can use (resistance training)'. Without those two, roughly 1/3 of the weight you drop is probably tissue you didn't want to lose.
Chapter 2
How much · 1.6-2.4 g/kg sweet spot
How much · 1.6-2.4 g/kg sweet spot
Mainstream recommendation: 1.6-2.4 g/kg/day during a cut, 1.2-1.6 g/kg during maintenance (Thomas 2016 ACSM sports nutrition position, Morton 2018 meta).
1.6 g/kg is the sweet spot identified by a 49-RCT meta-analysis:
Morton 2018 BJSM pooled 49 RCTs and 1863 subjects: above ~1.62 g/kg, strength and lean-mass gains plateau — additional protein isn't harmful but the curve flattens. This is the 'minimum effective dose' concept.
Why push the upper end (2.0-2.4 g/kg) during a deficit:
An energy deficit itself blunts muscle protein synthesis; higher protein 'pulls the signal' back upSatiety: protein is the most satiating of the three macros (raises PYY / glucagon-like peptide-1: A gut hormone released after eating that makes you feel full and helps lower blood sugar.)Highest thermic effect (TEF): 25-30% of protein calories are dissipated as heat (vs carbs 5-10% / fat 0-3%) — a built-in discountLongland 2016 used 2.4 g/kg
Concrete math (70 kg example):
Maintenance: 70 × 1.2 = 84 g/day (China EAR sits at 0.8 g/kg, too low)Recreational lifter: 70 × 1.6 = 112 g/dayCutting: 70 × 2.0 = 140 g/dayAggressive deficit + resistance (Longland protocol): 70 × 2.4 = 168 g/day
Older adults (50+) need more: baseline 1.2-1.6 g/kg (PROT-AGE consensus). Because of anabolic resistance — the same leucine dose triggers mechanistic target of rapamycin: The cell's master 'grow / build' switch — turned on by enough protein and resistance training. less effectively, so a higher stimulus is needed to clear threshold. 1.8-2.2 g/kg is safer during a cut.
Pregnancy / lactation / high-volume athletes: 1.8-2.5 g/kg is reasonable; don't drop below 1.2.
Safety (healthy kidney function):
Antonio 2015 fed healthy men 4.4 g/kg (~300 g/day) for 8 weeks: liver, kidney, and lipids all unchanged. 'High protein damages kidneys' has no RCT support in people with healthy renal function, only in pre-existing CKD. Don't cap protein at 1.0 g/kg based on hearsay — during a deficit that's giving up muscle preservation outright.
1.6 g/kg is the sweet spot identified by a 49-RCT meta-analysis:
Morton 2018 BJSM pooled 49 RCTs and 1863 subjects: above ~1.62 g/kg, strength and lean-mass gains plateau — additional protein isn't harmful but the curve flattens. This is the 'minimum effective dose' concept.
Why push the upper end (2.0-2.4 g/kg) during a deficit:
An energy deficit itself blunts muscle protein synthesis; higher protein 'pulls the signal' back upSatiety: protein is the most satiating of the three macros (raises PYY / glucagon-like peptide-1: A gut hormone released after eating that makes you feel full and helps lower blood sugar.)Highest thermic effect (TEF): 25-30% of protein calories are dissipated as heat (vs carbs 5-10% / fat 0-3%) — a built-in discountLongland 2016 used 2.4 g/kg
Concrete math (70 kg example):
Maintenance: 70 × 1.2 = 84 g/day (China EAR sits at 0.8 g/kg, too low)Recreational lifter: 70 × 1.6 = 112 g/dayCutting: 70 × 2.0 = 140 g/dayAggressive deficit + resistance (Longland protocol): 70 × 2.4 = 168 g/day
Older adults (50+) need more: baseline 1.2-1.6 g/kg (PROT-AGE consensus). Because of anabolic resistance — the same leucine dose triggers mechanistic target of rapamycin: The cell's master 'grow / build' switch — turned on by enough protein and resistance training. less effectively, so a higher stimulus is needed to clear threshold. 1.8-2.2 g/kg is safer during a cut.
Pregnancy / lactation / high-volume athletes: 1.8-2.5 g/kg is reasonable; don't drop below 1.2.
Safety (healthy kidney function):
Antonio 2015 fed healthy men 4.4 g/kg (~300 g/day) for 8 weeks: liver, kidney, and lipids all unchanged. 'High protein damages kidneys' has no RCT support in people with healthy renal function, only in pre-existing CKD. Don't cap protein at 1.0 g/kg based on hearsay — during a deficit that's giving up muscle preservation outright.
Chapter 3
Mechanism · protein leverage + mTOR
Mechanism · protein leverage + mTOR
Why is protein so special? Three mechanisms stack.
1. Protein Leverage Hypothesis (Simpson & Raubenheimer):
Humans require an absolute amount of protein, not a percentage. If dietary protein density is diluted (UPF typically < 12% energy from protein), the body will eat more total calories until protein is met — even if that means hundreds of extra kcal of carbs + fat. This is one underlying explanation for the modern obesity epidemic: the food industry diluted protein density, and people passively over-eat.
Used in reverse: push protein to 25-30% of total energy and appetite signals self-cap, total calories fall naturally. This is why high-protein diets cause weight loss even under ad-libitum conditions (Weigle 2005 classic RCT: raising protein from 15% to 30% had subjects spontaneously eat 441 kcal/day less).
2. Leucine threshold + mTOR complex 1: The main working form of mTOR — the switch that directly drives protein synthesis. activation (atlas L4 `leucine-threshold` + `mtor-pathway`):
Muscle protein synthesis (MPS) is not 'eat-and-build'; it's a threshold switch:
Per-meal leucine ≥ 2.5-3 g (≈ 25-30 g of high-quality protein, or 0.3-0.4 g/kg body weight) → mTORC1 activates → MPS runs for 90-120 minutesBelow threshold: MPS barely responds (older adults have higher thresholds, ~ 0.4 g/kg, due to anabolic resistance)Hitting threshold every meal vs same daily total but skewed distribution — the former gives a larger 24 h MPS AUC (Areta 2013)
Key implication: the daily total isn't enough — every meal must clear threshold. Breakfast 5 g + dinner 100 g ≠ three meals of 35 g.
3. Thermic effect of food (TEF) is 'free burn':
Protein TEF: 25-30% (100 kcal of protein → 25-30 kcal dissipated, 70-75 kcal net absorbed)Carb TEF: 5-10%Fat TEF: 0-3%
Replacing 100 kcal of carbs with protein → burns ~ 20 extra kcal/day. A 150 g vs 80 g protein day (same calories) → TEF differs by ~ 80-100 kcal/day. Combined with satiety, high protein means 'same calories, less net absorbed, more full'.
Why this matters more during a cut: an energy deficit upregulates AMP-activated protein kinase: The cell's 'low fuel' sensor — switches on when energy is low to make energy and pause building. and suppresses mechanistic target of rapamycin: The cell's master 'grow / build' switch — turned on by enough protein and resistance training. (energy-saving signal). Under those conditions only a strong leucine pulse can pull MPS back up. Insufficient protein = letting the body default to breaking down muscle while in energy-saving mode.
1. Protein Leverage Hypothesis (Simpson & Raubenheimer):
Humans require an absolute amount of protein, not a percentage. If dietary protein density is diluted (UPF typically < 12% energy from protein), the body will eat more total calories until protein is met — even if that means hundreds of extra kcal of carbs + fat. This is one underlying explanation for the modern obesity epidemic: the food industry diluted protein density, and people passively over-eat.
Used in reverse: push protein to 25-30% of total energy and appetite signals self-cap, total calories fall naturally. This is why high-protein diets cause weight loss even under ad-libitum conditions (Weigle 2005 classic RCT: raising protein from 15% to 30% had subjects spontaneously eat 441 kcal/day less).
2. Leucine threshold + mTOR complex 1: The main working form of mTOR — the switch that directly drives protein synthesis. activation (atlas L4 `leucine-threshold` + `mtor-pathway`):
Muscle protein synthesis (MPS) is not 'eat-and-build'; it's a threshold switch:
Per-meal leucine ≥ 2.5-3 g (≈ 25-30 g of high-quality protein, or 0.3-0.4 g/kg body weight) → mTORC1 activates → MPS runs for 90-120 minutesBelow threshold: MPS barely responds (older adults have higher thresholds, ~ 0.4 g/kg, due to anabolic resistance)Hitting threshold every meal vs same daily total but skewed distribution — the former gives a larger 24 h MPS AUC (Areta 2013)
Key implication: the daily total isn't enough — every meal must clear threshold. Breakfast 5 g + dinner 100 g ≠ three meals of 35 g.
3. Thermic effect of food (TEF) is 'free burn':
Protein TEF: 25-30% (100 kcal of protein → 25-30 kcal dissipated, 70-75 kcal net absorbed)Carb TEF: 5-10%Fat TEF: 0-3%
Replacing 100 kcal of carbs with protein → burns ~ 20 extra kcal/day. A 150 g vs 80 g protein day (same calories) → TEF differs by ~ 80-100 kcal/day. Combined with satiety, high protein means 'same calories, less net absorbed, more full'.
Why this matters more during a cut: an energy deficit upregulates AMP-activated protein kinase: The cell's 'low fuel' sensor — switches on when energy is low to make energy and pause building. and suppresses mechanistic target of rapamycin: The cell's master 'grow / build' switch — turned on by enough protein and resistance training. (energy-saving signal). Under those conditions only a strong leucine pulse can pull MPS back up. Insufficient protein = letting the body default to breaking down muscle while in energy-saving mode.
Chapter 4
Practice · 25-40 g across 3-4 meals
Practice · 25-40 g across 3-4 meals
Core rule: per meal 0.3-0.4 g/kg = 25-40 g of high-quality protein, 3-4 meals/day, 3-5 h apart (lets MPS finish one cycle and settle).
Sample day (70 kg, target 140 g/day):
Breakfast 35 g: 2 whole eggs (12 g) + 200 g Greek yoghurt (20 g) + 1 scoop whey (3 g)Lunch 40 g: 150 g chicken breast / fish (35 g) + 100 g chickpeas (7 g)Snack 25 g (post-workout): 25 g whey or 200 g cottage cheeseDinner 40 g: 150 g beef / salmon / tofu (30 g) + side with legumes (10 g)
The first 30 g of protein after waking matters most:
Overnight fast → muscle is in a net breakdown state (low CHO + amino acids)Protein at meal 1 → MPS fires immediately, closes the catabolic window earlySkipping breakfast → first meal pushed to afternoon = 4-6 extra hours of breakdownAnti-pattern: 'carb breakfast + carb lunch + protein dinner' = most of the day MPS doesn't respond
Refuel within 2 hours post-workout:
The 'anabolic window' isn't as tight as 30 minutes — actually ~ 2-4 hours (Aragon & Schoenfeld review)But 20-40 g protein post-training does amplify the MPS responsePractical: full meal within 1 h, or whey scoop then real meal 1 h later
High-quality sources (sorted by leucine density + absorption rate):
Whey: leucine ~ 11% / fastest absorption / first pick post-workout / 25 g whey ≈ 2.7 g leucine (right at threshold)Eggs: whole-egg leucine ~ 8.5% / complete AA profile + choline + vitamin D / breakfast pickFish (salmon / tuna / cod): high protein + ω-3 / anti-inflammatory + CV co-benefitLean red meat (beef / pork loin): protein + iron + B12 + creatine / 2-3×/weekGreek yoghurt / cottage cheese: casein releases slowly, ideal pre-bed to sustain overnight MPSSoy products (tofu / edamame / soy isolate): the one plant source close to animal protein, leucine ~ 8%
Vegetarian / vegan amino-acid completeness:
Single plant proteins usually lack one limiting amino acid: grains (rice / wheat) low in lysine, legumes low in methionineCombine across one meal: grains + legumes (rice + beans / pita + chickpeas / whole-wheat + peanut butter) covers the spectrumSoy + quinoa + amaranth are the few inherently complete plant proteinsVegetarians should target 1.8-2.2 g/kg: plant protein digestibility (DIAAS) is 20-30% lower than animal, real availability discounts accordinglyWhen needed, soy / pea / rice isolate powder is a basic tool, not a luxury
Atlas connections:
weight-management-foundations (the cut framework)adaptive-thermogenesis (the RMR-drop counterpart)leptin-set-point (hunger-signal management)protein (base node) + protein-and-lifting (training synergy)L4 `leucine-threshold` + `mtor-pathway` (mechanism deep-dive)
Sample day (70 kg, target 140 g/day):
Breakfast 35 g: 2 whole eggs (12 g) + 200 g Greek yoghurt (20 g) + 1 scoop whey (3 g)Lunch 40 g: 150 g chicken breast / fish (35 g) + 100 g chickpeas (7 g)Snack 25 g (post-workout): 25 g whey or 200 g cottage cheeseDinner 40 g: 150 g beef / salmon / tofu (30 g) + side with legumes (10 g)
The first 30 g of protein after waking matters most:
Overnight fast → muscle is in a net breakdown state (low CHO + amino acids)Protein at meal 1 → MPS fires immediately, closes the catabolic window earlySkipping breakfast → first meal pushed to afternoon = 4-6 extra hours of breakdownAnti-pattern: 'carb breakfast + carb lunch + protein dinner' = most of the day MPS doesn't respond
Refuel within 2 hours post-workout:
The 'anabolic window' isn't as tight as 30 minutes — actually ~ 2-4 hours (Aragon & Schoenfeld review)But 20-40 g protein post-training does amplify the MPS responsePractical: full meal within 1 h, or whey scoop then real meal 1 h later
High-quality sources (sorted by leucine density + absorption rate):
Whey: leucine ~ 11% / fastest absorption / first pick post-workout / 25 g whey ≈ 2.7 g leucine (right at threshold)Eggs: whole-egg leucine ~ 8.5% / complete AA profile + choline + vitamin D / breakfast pickFish (salmon / tuna / cod): high protein + ω-3 / anti-inflammatory + CV co-benefitLean red meat (beef / pork loin): protein + iron + B12 + creatine / 2-3×/weekGreek yoghurt / cottage cheese: casein releases slowly, ideal pre-bed to sustain overnight MPSSoy products (tofu / edamame / soy isolate): the one plant source close to animal protein, leucine ~ 8%
Vegetarian / vegan amino-acid completeness:
Single plant proteins usually lack one limiting amino acid: grains (rice / wheat) low in lysine, legumes low in methionineCombine across one meal: grains + legumes (rice + beans / pita + chickpeas / whole-wheat + peanut butter) covers the spectrumSoy + quinoa + amaranth are the few inherently complete plant proteinsVegetarians should target 1.8-2.2 g/kg: plant protein digestibility (DIAAS) is 20-30% lower than animal, real availability discounts accordinglyWhen needed, soy / pea / rice isolate powder is a basic tool, not a luxury
Atlas connections:
weight-management-foundations (the cut framework)adaptive-thermogenesis (the RMR-drop counterpart)leptin-set-point (hunger-signal management)protein (base node) + protein-and-lifting (training synergy)L4 `leucine-threshold` + `mtor-pathway` (mechanism deep-dive)